Nichole,
Sorry to hear about your pain. The Charite is no longer an experimental surgery. It was approved by the FDA in 2004. Your insurance company has been misled or they haven't updated their records yet. Remind them a fusion would be double the cost.
Dr. Jay Williams will be performing the Charite surgery in Seattle. Look for him at this link.
http://www.proliancesurgeons.com/594.html
I had L5S1 Charite surgery in Europe. After returning to the US I was under Dr. Williams' care until I moved away from Seattle last year. He's knows the technology and he's very good at explaining things. Please go see him (top floor of Nordstrom building on Pill Hill).
All the best,
Jim